input: sensors: fix deadlock issue during accelerometer disabling.

Accelerometer mma8x5x driver may struck in disabling procedure due
to deadlock on workqueue flush.

Change-Id: Ibcd6ebe92bc2fece459fde5f76e5bfe1f90586a0
Signed-off-by: Bingzhe Cai <bingzhec@codeaurora.org>